Test Procedures for new Designs

The counterpoint to a specification is a test procedure. With a specification and an incoming test procedure, a client can have assurance that he gets what he orders.

There are actually three types of test procedures we are concerned with here

• Debug Test procedure - developed by AirBorn to debug the design
• Incoming Test procedure - developed by Client to test AirBorn's work
• Manufacturing Test procedure - developed by Manufacturer/Client/Airborn to test units as they are produced

Debug Test procedure

The debug test procedure will be developed by AirBorn Electronics as the design proceeds. Its aim is to divide the testing of the design into small, autonomous units. In this respect the debug test is providing a tool for the detection of faults in the design in a way that most conveniently allows them to be fixed - by finding them in isolation.

The debug test procedure will pay particular attention to suspected trouble spots in a design. For instance, if an analog input is known to be operating at a particularly low input signal level, a debug test procedure might include noise measurement, thermal drift testing, and evaluation of potential cross talk sources.

The debug test procedure will normally also include an overall functional test, based on the specification. This is basically equivalent to the incoming test procedure applied by the client.

Incoming Test procedure

The clients incoming test procedure will normally start with the specification of the product and test that the specified features are actually delivered. This testing may be a repeat of part of the debug test procedure carried out by AirBorn Electronics. Some of our clients choose to accept our test results and not to use an Incoming test procedure of their own. Other clients are constrained by ISO9000 to performing an incoming test, however the test procedures that we have already followed can prove a useful model for their own tests.

The incoming test procedure has different objectives from the debug test procedure - its aim is to prove that the design meets the specification. Overall tests are usually good for this objective. The debug test procedure is attempting to isolate any faults in the design. This requires testing by section and thorough characterisation of the design rather than just meet spec/miss spec results.

Manufacturing Test procedure

The manufacturing test procedure is used to test product as it is being manufactured. It would be unusual for the manufacturing test procedure to be based on either the debug test procedure or the clients incoming test procedure, unless the production quantity was small. The procedure is quite dependent on the manufacturer, his production techniques, and his testing equipment.

The manufacturing test procedure is an economics driven test. The procedure is designed to save money for the manufacturer.

For instance, depending on the application of the equipment, it would be possible to deliver all circuitry completely untested, and indeed this is the aim of many IS09000 manufacturing flows. However, any failures would incur a financial cost, both in terms of returns, rework & replacement, and also the clients reputation. In the case of the extremes: a cheap toy, or superlative manufacturing with very few defects, no testing is an option. The aim, otherwise, is to find a manufacturing test procedure which reduces the outgoing failure rate while not costing more than it saves.

A man can fail many times, but he isn't a failure until he begins to blame somebody else. --John Burroughs

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